How to print the Execution Plan for batch processing in Flink?

Question

I created a Java program with Flink that multiply 2 matrices. I am using the batch (DataSet) environment to process it and I want to show the execution plan for this. When I did some stream (DataStream) example I just called StreamExecutionEnvironment.getExecutionEnvironment().getExecutionPlan() . Flink has the same method available for batch but when I call it I get the error: java.lang.RuntimeException: No new data sinks have been defined since the last execution. The last execution refers to the latest call to 'execute()', 'count()', 'collect()', or 'print()'. java.lang.RuntimeException: No new data sinks have been defined since the last execution. The last execution refers to the latest call to 'execute()', 'count()', 'collect()', or 'print()'. . I guess I am doing what is exactly described here: https://ci.apache.org/projects/flink/flink-docs-stable/dev/execution_plans.html but for some reason, I am getting the exception.

import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.common.functions.MapPartitionFunction;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.api.java.tuple.Tuple3;
import org.apache.flink.api.java.tuple.Tuple4;
import org.apache.flink.util.Collector;

public class MatrixMultiplication {

    private static final String MATRIX_A = "A";
    private static final String MATRIX_B = "B";
    public MatrixMultiplication() throws Exception {

        final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

        DataSet<Tuple4<String, Integer, Integer, Integer>> matrixA = env.readCsvFile("resources/matrixA.csv")
                .fieldDelimiter(",").types(Integer.class, Integer.class, Integer.class)
                .map(t -> new Tuple4<String, Integer, Integer, Integer>("A", t.f0, t.f1, t.f2))
                .returns(Types.TUPLE(Types.STRING, Types.INT, Types.INT, Types.INT));
        System.out.println("Matrix A");
        matrixA.print();

        DataSet<Tuple4<String, Integer, Integer, Integer>> matrixB = env.readCsvFile("resources/matrixB.csv")
                .fieldDelimiter(",").types(Integer.class, Integer.class, Integer.class)
                .map(t -> new Tuple4<String, Integer, Integer, Integer>("B", t.f0, t.f1, t.f2))
                .returns(Types.TUPLE(Types.STRING, Types.INT, Types.INT, Types.INT));
        System.out.println("Matrix B");
        matrixB.print();

        int columnsMatrixB = 2;
        int linesMatrixA = 2;

        DataSet<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> keyValueMatrixA = matrixA
                .mapPartition(new MapMatrixToKeysAndValues(columnsMatrixB));

        DataSet<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> keyValueMatrixB = matrixB
                .mapPartition(new MapMatrixToKeysAndValues(linesMatrixA));
        DataSet<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> matrixAB = keyValueMatrixA.union(keyValueMatrixB);
        DataSet<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> matrixAB_01 = matrixAB.groupBy(0)
                .reduce(new ProductReducer());

        DataSet<Tuple2<Tuple2<Integer, Integer>, Integer>> matrixAB_02 = matrixAB_01.map(new SumMapper());

        DataSet<Tuple2<Tuple2<Integer, Integer>, Integer>> productMatrixAB = matrixAB_02.groupBy(0)
                .reduce(new SumReducer());
        System.out.println("Matrix AB");
        productMatrixAB.print();

        // String executionPlan = env.getExecutionPlan();
        // System.out.println("ExecutionPlan ........................ ");
        System.out.println(productMatrixAB.getExecutionEnvironment().getExecutionPlan());
        // System.out.println("........................ ");
    }

    public static class MapMatrixToKeysAndValues implements
            MapPartitionFunction<Tuple4<String, Integer, Integer, Integer>, Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> {

        private static final long serialVersionUID = 6992353073599144457L;
        private int count;

        public MapMatrixToKeysAndValues(int count) {
            this.count = count;
        }

        @Override
        public void mapPartition(Iterable<Tuple4<String, Integer, Integer, Integer>> values,
                Collector<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> out) throws Exception {

            for (Tuple4<String, Integer, Integer, Integer> tuple : values) {
                for (int c = 1; c <= count; c++) {

                    Tuple3<Integer, Integer, Integer> key = null;
                    Integer value = null;

                    if (MATRIX_A.equals(tuple.f0)) {
                        // key(i,k,i+j) for k=1...N
                        Integer i = tuple.f1;
                        Integer j = tuple.f2;
                        Integer k = c;
                        key = new Tuple3<Integer, Integer, Integer>(i, k, i + j);

                        // value matrix[i,j]
                        value = tuple.f3;
                    } else if (MATRIX_B.equals(tuple.f0)) {
                        // key(i,k,i+j) for i=1...L
                        Integer i = c;
                        Integer j = tuple.f1;
                        Integer k = tuple.f2;
                        key = new Tuple3<Integer, Integer, Integer>(i, k, i + j);

                        // value matrix[j,k]
                        value = tuple.f3;
                    }
                    out.collect(new Tuple2<Tuple3<Integer, Integer, Integer>, Integer>(key, value));
                }
            }
        }
    }

    public static class ProductReducer implements ReduceFunction<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>> {

        private static final long serialVersionUID = 6166767956669902083L;

        @Override
        public Tuple2<Tuple3<Integer, Integer, Integer>, Integer> reduce(
                Tuple2<Tuple3<Integer, Integer, Integer>, Integer> value1,
                Tuple2<Tuple3<Integer, Integer, Integer>, Integer> value2) throws Exception {

            Integer product = null;
            product = value1.f1 * value2.f1;

            return new Tuple2<Tuple3<Integer, Integer, Integer>, Integer>(value1.f0, product);
        }
    }

    public static class SumMapper implements
            MapFunction<Tuple2<Tuple3<Integer, Integer, Integer>, Integer>, Tuple2<Tuple2<Integer, Integer>, Integer>> {

        private static final long serialVersionUID = -1437482917757334157L;

        @Override
        public Tuple2<Tuple2<Integer, Integer>, Integer> map(Tuple2<Tuple3<Integer, Integer, Integer>, Integer> value)
                throws Exception {

            Tuple2<Integer, Integer> key = new Tuple2<Integer, Integer>(value.f0.f0, value.f0.f1);
            return new Tuple2<Tuple2<Integer, Integer>, Integer>(key, value.f1);
        }
    }
    public static class SumReducer implements ReduceFunction<Tuple2<Tuple2<Integer, Integer>, Integer>> {

        private static final long serialVersionUID = 7849401047616065465L;

        @Override
        public Tuple2<Tuple2<Integer, Integer>, Integer> reduce(Tuple2<Tuple2<Integer, Integer>, Integer> value1,
                Tuple2<Tuple2<Integer, Integer>, Integer> value2) throws Exception {

            Tuple2<Integer, Integer> key = new Tuple2<Integer, Integer>(value1.f0.f0, value1.f0.f1);
            Integer value = value1.f1 + value2.f1;

            return new Tuple2<Tuple2<Integer, Integer>, Integer>(key, value);
        }
    }
}

$ cat resources/matrixA.csv

1,1,1
1,2,3
1,3,4
1,4,-2
2,1,6
2,2,2
2,3,-3
2,4,1

$ cat resources/matrixB.csv

1,1,1
1,2,-2
2,1,4
2,2,3
3,1,-3
3,2,-2
4,1,0
4,2,4

Answer 1

The plan should be printed if you remove the print() calls.

print() also triggers an execution.